This invention relates to an absorption refrigerator of natural circulation type employing water as a refrigerant and an aqueous solution of a lithium salt as an absorbing medium. More particularly, this invention relates to an absorption refrigerator of natural circulation type in which low-temperature energy is utilized as a heat source for the generator.
U.S. Pat. No. 2,282,503 discloses a prototype of absorption refrigerators of natural circulation type with which the present invention is concerned. The refrigerator disclosed in the U.S. patent above cited employs water as a refrigerant and a lithium salt such as lithium chloride or lithium bromide as an absorbing medium, and these salts are present in the form of an aqueous solution thereof in the refrigeration system.
In the absorption refrigerator of natural circulation type referred to above, the aqueous solution of the lithium salt is heated to boil in a generator and is lifted through a gas-liquid lift into a separator located at an upper level according to the principle of an air lift pump, and the solution is separated into water vapor and the residual concentrated lithium salt solution in the separator. This water vapor is subsequently cooled to condense in a condenser, and the condensate or water is fed to an evaporator. The water fed to the evaporator is vaporized again since the internal pressure of the evaporator is sufficiently low to such an extent that the water can be readily vaporized. Due to the fact that vaporization of the water takes heat and thus produces cooling, another liquid flowing through the evaporator is cooled and this cooled liquid is suitably utilized as a source of refrigeration.
In the meantime, the concentrated lithium salt solution separated from the water vapor in the separator is supplied to a heat exchanger to be subject to heat exchange with a dilute lithium salt solution described later, and the concentrated lithium salt solution thus cooled down to a low temperature is then fed to an absorber. In the absorber, this concentrated lithium salt solution absorbs the water vapor produced in the evaporator to turn into a dilute lithium salt solution. This dilute lithium salt solution is subsequently fed to the heat exchanger to be subject to heat exchange with the concentrated lithium salt solution as above described, and the dilute lithium salt solution thus heated as a result of the heat exchange is returned to the generator again. The cycle above described is repeated to carry out the desired refrigeration.
The function of the generator disposed in the lower part of the prior art absorption refrigerator of natural circulation type has thus been such that the generator acts to lift the dilute lithium salt solution into the separator disposed thereabove and heat is applied to the lower portion of the generator so that the concentrated lithium salt solution of desired concentration can be obtained in this separator. In other words, heating has been carried out at such a temperature which is enough to overcome both the resistance of the gas-liquid lift against liquid flow and the pressure difference due to the height of the gas-liquid lift. A heat source of high temperature such as a source of steam or oil burner has been employed hitherto to heat the generator since a high temperature can easily be obtained with such a heat source. It is presently strongly demanded from the viewpoint of economical utilization of energy to operate absorption refrigerators of natural circulation type by a heat source of low temperature such as warm water obtained by a solar heat collector or warm waste water discharged from factories. However, the prior art absorption refrigerator of natural circulation type has been unable to operate with such a low-temperature heat source.